Surface Engineering of Ni wires and Rapid Growth Strategy of Ni‐MOF Synergistically Contribute to High‐Performance Fiber‐Shaped Aqueous Battery

Abstract The fiber‐shaped aqueous battery (FSAB) has the advantages of flexibility, portability and safety making it promising for energy storage applications. In particular, FSABs based on metal wire current collectors with good electrical conductivity can provide excellent energy storage properties. However, the low adhesion caused by the smooth surface of the metal wire and the unavailability of many electrochemically active materials for use in FSAB is holding back their development. Herein, a substrate is effectively constructed for the strongly applicable growth of the active material via a Ni wire etching strategy. In addition, core‐shell structured nanorod arrays consisting of NiCo 2 O 4 and Ni‐metal–organic frameworks (MOFs) are constructed, where Ni‐MOF can be obtained rapidly via β‐Ni(OH) 2 intermediates. The NCO/NM‐15 electrode obtained by structural regulation exhibits high capacity and outstanding cycling stability. De calculations further demonstrate that the formation of NiCo 2 O 4 and Ni‐MOF heterostructures results in a significant increase in the Fermi level leading to more active internal electrons, which facilitates electron transfer in electrochemical reactions. An assembled FSAB device can provide an energy density of 158.33 µWh cm −2 and the devices can provide power for a calculator and an electronic watch screen, demonstrating a wide application prospect in the field of energy storage.